This invention relates to a method of and apparatus for processing heat-softened material, such as glass, and more especially to a method and arrangement of feeding heat-softened glass to a stream feeder or bushing in a manner that thermally conditions the glass.
In a typical direct melt operation, glass batch is reduced to a molten state and refined in a furnace. The refined glass is flowed through a forehearth channel to openings in bottom of the channel. The glass flows downwardly through the openings to electrically heated stream feeders or bushings disposed in spaced relation along the forehearth. Streams of glass flow through orifices in the bushings and the streams are attenuated to filaments or fibers by well-known methods.
As the glass flows downward from the forehearth through a flow block and a bushing block into a bushing, a temperature gradient is produced in the molten glass. This temperature gradient can be caused by the flow block and the bushing block acting as heat sinks which cool the glass. The difference in temperature of the glass at the bushing block and the glass at the center of the passage in the bushing block can be 100.degree. F. or more. Such glass, having a large temperature gradient, entering a bushing during the operation of the fiber forming process can cause a non-uniform heat pattern across the bottom plate of the bushing and an inefficient fiber forming operation. Such glass entering a fiber forming bushing can result in the production of fibers which do not meet processing specifications and can result in process interruptions.